This happens to me most every time I have a panic attack. I think of the closet door that's behind me when I'm sitting at the computer, or of a person lurking in the laundry room, or Stephen King's damned clown from It climbing out of the shower drain, and away it goes. And once it gets started it usually gets worse because I keep anticipating some sort of attack, or stabbing. Most of the time I just let them be instead of trying to control them, since that usually makes it worse anyway. XP

Though sometimes, if I realize that it's getting bad before it gets to be too much for me to reign in, I start singing whatever's stuck in my head at the time, or thinking about something I could possibly write with a few of my newer story characters, or find a word game to play, name as many words that start with a certain letter of the alphabet as I can.Homo Sapien suggested to me to keep my mind occupied, and do something mentally stimulating, and it seems to work alright if I catch it quick. When you start to have thoughts of something that sends you into a spiral, distract yourself. Pick up a book. Sing a song. Do something that will get your mind off of it.

Hope this helps. ^^